Method and equipment for mangling wet laundry

ABSTRACT

In the case of common trough mangles (1) used for the smoothing and drying of wet laundry pieces (11) wherein the hollow rollers (2) provided with roller wrappings (3) are only partially surrounded by heated pressing troughs (4, 5), a considerable amount of energy is wasted due to the absorption of cooler room air. In order to eliminate the cause of this deficiency, the invention proposes to cover the free area of the hollow roller (2) with a hood (6), whose rims (9) are sealed against the roller wrapping (3). The exhaust (8) of the steam is removed directly from the hood (6). This way, inside the hood (6) clean saturated steam is obtained and superheated, when the absorption from the hood (6) takes place in counterflow with regard to the travel of the laundry pieces (11). This superheated saturated steam is especially suitable as operating means for washing machines or the like.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Phase Application corresponding toPCT/EP/83/00257 filed Oct. 3, 1983 and based upon German application No.P 32 36 870.4 filed Oct. 5, 1982 under the International Convention.

FIELD OF THE INVENTION

The invention relates to methods and devices for mangling wet laundrywhich is conveyed between at least one hollow roller, provided with aroller wrapping and which can be perforated and connected to an exhaustinstallation, and a heated bearing surface in the shape of atrough-shaped hollow body wherein the bearing surface encompasses onlyone portion of the hollow roller, the other portion being covered by ahood, sealed with respect to the roller wrapping.

BACKGROUND OF THE INVENTION

In the trough mangles existing on the market the padded hollow roller isencompassed by the bearing surfaces over an arc of its circumference ofat least 165°. During the drying of the laundry, the resulting steam isevacuated by a frontally attached blower through the roller wrapping aswell as through a multitude of holes in the steel wall of the hollowroller. These blowers have to be arranged to handle the steam generatedby a maximum mangling load. Since the blowers are dimensioned with asafety factor with relation to the delivery (negative pressure) anddischarge, even with maximum mangling loads a negative pressure canprevail inside the hollow roller (pressing roller) which results in theintake of cool room air through the free surface of the roller wrappingnot covered by the bearing surfaces. The free surface comprisesapproximately 195° of arc of the roller wall.

If the mangling is performed with little laundry or with interruptionswhen there is no laundry to be pressed, then, due to the exhaustresulting from the rotational speed of the hollow roller, energy iswasted. In this case, air at room temperature is drawn in through theturning hollow roller, cools it on its way to discharge from thepressing trough to the reentry and the drying speed is reduced byapproximately 10-15% while additional energy in the form of steam mustbe fed to the pressing trough as required for heating this air.

It is therefore required for 1 kg laundry having a normal residualmoisture at the mangling loading rate of 40 to 60% which is common inpractice to provide an amount of steam of 1.2 kg or more for heating themangle. The thermal efficiency is consequently in the range of 50% orless.

Numerous proposals aimed at reducing the energy consumption in suchcommon mangles have been published. For instance it has been proposed tocover the roller wrapping with a shell extending at a distance ofapproximately 3 cm from the surface of the roller wrapping and parallelthereto. This can affect only a slight reduction in energy consumptionbecause the heating of the room air at the hot surfaces on the upperside of the mangle heat radiation are reduced.

Due to the fact that the shell is positioned at a distance from theroller wrapping it is possible for equal amounts of the room air, as inthe fully open pressing roller, to be drawn in through the larger slotsat the entrance and exit ends having a cross section of approximately 1sqm. This room air will then be unnecessarily blown out as hot air.Since the cross section of the suction connection on the pressing rolleris considerably smaller than the cross section of the mentioned slots,the surface of the pressing roller is disadvantageously provided withroom air.

The German open application No. 19 37 738 tries to eliminate thisdisadvantage proposing that the feed- and discharge-end rims of a shellshaped as a hood with reflector be sealed opposite to the rollerwrapping. Since the steam generated during mangling must be exhaustedfrom the drum axially, the construction of heat-resistant bearings of alarger diameter and the high cost related thereto are unavoidable. Thesealing of the hood against the roller wrapping leads to workinterruptions and the related drops in temperature to corrosion,requiring considerable added expenses for adequate countermeasures toavoid that.

OBJECT OF THE INVENTION

The object of the invention is to achieve energy savings in aneconomical way and to utilize the saved energy in a method and apparatusfor mangling wet laundry.

SUMMARY OF THE INVENTION

This object is attained through the method according to the invention,in that the steam originating from the laundry or the roller wrappingwhile passing the bearing surface is led into the interior of the hoodand is therefrom evacuated through an exhaust device directly attachedto the hood.

A particular embodiment of the invention, which can be an independentfeature in itself, consists in that the saturated steam resulting at themangle is conveyed with the best possible exclusion of air admixture andused as an operating medium at the washing machines of the laundry, fortheir direct heating, with the aid of compression and in some cases withthe aid of periodic superheating.

The invention is based on the concept that basic energy savings areobtainable by eliminating as much as possible the intake of fresh airthrough the free surface of the hollow roller not surrounded by thepressing trough. If the free surface is surrounded by the sealed hoodaccording to the invention and connected to the exhaust installation,the output of the blower can be reduced to 60% of that otherwiserequired. The evacuation of the steam produced during drying can becarried out therefore directly from the hood, since in the case of thecommon springpressor elastopress flexible wrapping of the hollowcylinder a sufficiently large exhaust cross section exists between thefabric coating and roller shell. Therefore it is possible to leave theshell of the roller without holes. On the contrary, if a perforatedroller shell without axial suction connections is used, the absorptionof the steam through the hood is further facilitated. Since the directsuction according to the invention is almost only used to eliminate thesteam produced during drying and for this purpose a 5 to 7 times largercross section is available, the negative pressure produced by the blowercan be significantly reduced, namely to about 35% of the presentnegative pressure.

Consequently, a low-pressure blower can be installed with the advantagethat when the mangle runs without load and also when the amount of steamis equal to 0, less infiltrated air is absorbed through the free rollersurface which remains between the hood and the pressing trough.

A considerable cost saving also results from the fact that in the caseof the commonly known installation the usual axial connection of theexhaust to the hollow shaft of the hollow roller is superfluous, whichallows for smaller less expensive bearings for the hollow roller.

An advantage of a different kind regarding the direct abstraction of thesteam from the hood arises from the fact that the steam generated in thetrough area penetrates the textile material at the outer surface of thewrapping from the exterior towards the interior and escapes again fromthe interior towards the exterior in the hood area. This alternate flowthrough the textile material keeps its pores open remarkably longer. Inthe mangles known in the art the air is always directed from theexterior to the interior through the finishing textile, which results ina filtering effect for room air rich in lint and dust particles.Consequently the finishing wrapping becomes more dense with increasedoperation time and eventually steamproof, necessitating more frequentwashing. These disadvantages are eliminated by the invention.

Up to now, the prevailing concept in the field was that it was necessaryto feed to the mangle certain amounts of air in order to dry thecovering of the roller wrapping and then to be able to carry away thesteam generated in the mangle. Even the newest proposals (open Germanapplication Nos. 30 44 229, 31 23 886, 32 09 365) deal with variouspossible solutions for supplying the mangle with air.

The invention makes a clean break with these earlier solutions by tryingto keep the air away or even to eliminate it completely in order to keepthe steam generated in the mangle as clean as possible and to utilizeit. Since steam is absorbed at the entrance side of the hood, there isalready superheated steam at this point, while at the opposite side ofthe hood saturated steam is still available. The superheating of thesteam results advantageously from the countercurrent movement wherebythe laundry passes the mangle in a counterflow with respect to the steamabsorption flow. The saturated steam originally generated in the mangleduring its countercurrent absorption movements sweeps heated metal partsof the rollers, troughs, and the hood, thereby becoming superheated,which again leads to the drying of the roller coverings with overheatedsteam. Surprisingly it has been proven this way that there is no needfor air either as a drying or as a conveying means and indeed an airsupply would be rather damaging.

In the concept of one of the embodiments of the invention, thesuperheated steam generated during mangling utilized according to theinvention, is supplied to the washing machines as a direct heatingmedium which can also be superheated.

A comparative energy calculation has shown that by supplying the washingmachine and the mangle with steam, approximately 50% fresh steam can besaved when the washing machine is supplied with superheated steamproduced during mangling.

In conclusion, by applying the method in accordance with the invention,the drying speed is increased, the energy saving considerably improvedand the thermal efficiency rate significantly increased. A considerablyshorter heat-up time of the mangle with less energy consumption results.The heat transfer to the room is remarkably decreased, as is its idlingconsumption. In order to achieve these savings it is not necessary touse the expensive heat exchangers required by the current state of theart.

BRIEF DESCRIPTION OF THE DRAWING

Embodiments of the invention are represented schematically in thedrawing, in which:

FIG. 1 is a diagrammatic cross section through a mangle trough with hoodunder no-load conditions;

FIG. 2 is a cross section of the apparatus of FIG. 1 with introducedlaundry;

FIG. 3 is a cross section through a mangle consisting of severalpressing troughs and hollow rollers;

FIG. 4 is an illustration of the connected arrangement of mangle andwashing machine; and

FIG. 5 is an illustration of a flat press to stress the application ofthe invention to other laundry processing machines.

SPECIFIC DESCRIPTION

The basic concept of the invention is illustrated in FIG. 1, with atrough mangle 1. This has a rotatable hollow cylinder 2 which does nothave to have any roller perforations, but can also be provided with onesuch perforation. This hollow roller 2 is surrounded by a yieldable,steam permeable roller wrapping 3, shaped in the usual manner. A portionof the roller wrapping 3 is encompassed by a trough shaped hollow body4, having a heated working surface 5 through which the thermal energyneeded for the drying and smoothing of the laundry 11 is provided.

The portion of the hollow cylinder 2, respectively of its rollerwrapping 3 which is not encompassed by or juxtaposed with thetrough-shaped hollow body 4 is surrounded by a hood 6, whose interiorspace 7 is sealed with respect to roller wrapping 3 by means of theseals 9. An exhaust connection 8 is attached to the hood 6.

As shown in FIG. 1, the room air can reach the roller wrapping 3 only inthe most minimal amounts along the narrow air duct 10 and from therethrough the interior of the roller wrapping the air can reach the innerspace 7 of the hood 6 and from there can be absorbed. It is thereforeenough to have only a low pressure blower to keep the infiltrated airaway from entering the free space of the roller surface between the hood6 and the trough 4, while the mangle is in no-load condition and steamis not generated.

If, on the contrary, a piece of laundry 11 is processed, as shown inFIG. 2, practically only a negligible amount of infiltrated air is drawnin. Instead the steam generated by the heating of the piece of laundry11 at the working surface 5 is abstracted in the direction of the flowindicated by arrows 12 from the inner space of roller wrapping 3, fromwhere the steam due to its expansion easily reaches the inner space 7 ofthe hood 6 and from there said steam is drawn through the exhaust 8. Ifthe shell of the hollow roller 2 is perforated, the flow takes placealso in a somewhat radial direction through the hollow roller 2.

In the case of equal pressure or even slight overpressure in the hood 6with respect to its surroundings it is possible to eliminate completelythe infiltrated air. The blower is then so adjusted (as to the number ofrotations) that with different steam amounts the pressure in the manglecan be maintained at the same level.

When the trough mangle 1 according to FIG. 3 has several hollow rollers2 and trough-shaped hollow bodies 4, it is suitable to provide a singlehood 6 which encompasses all the hollow cylinders 2 and accordingly alsoonly one exhaust connection. In this case, the seal 9 is mountedsuitably only at the entrance side of the first hollow cylinder 2 or thefeeding conveyor and at the exit side of the last hollow cylinder 2 orthe discharge conveyor.

Advantageously, the exhaust connections 8 are mounted at the entranceside of the hood 6. This answers a countercurrent motion between thepiece of laundry 11 and the absorption flow 12. The steam generatedduring the drying of the piece of laundry 11 appears first as saturatedsteam. In the course of the flow 12, this saturated steam gets heatedthrough its contact with the exposed metal parts and reaches the area ofthe exhaust connection 8 as an energy source of high value, ready forutilization.

FIG. 4 shows in this context an advantageous embodiment for the saidenergy utilization. A washing machine 17, which needs energy and heatfor its washing operation, is connected via a conveyor 18 with themangle 1 which in this instance has three rollers 2. The spread piece oflaundry 11 is fed through the sealed feeding slot 9 of the mangle 1. Thesaturated steam collected during mangling is concentated in the hood 6and therefrom absorbed in a counterflow and exhausted at 8 in asuperheated condition.

FIG. 5 shows an alternative to the embodiment of FIGS. 1, 2 and 3. Thedrying process according to the invention is suited not only formangles, but generally for contact drying. FIG. 5 shows a contact press26 which has a level heating plate 23, against which the laundry piece11 is pressed with the aid of a belt conveyor 25 and several pressurerollers 24. The contact press 26 is surrounded on the outside by thehood 6, whose inner space 7 is secured against air infiltration by seals9. In this embodiment, as well as in the aforedescribed embodiments, itis normal to seal the hood not only in the direction of the conveyor,but also laterally, for instance against the hollow body 4 or theheating plate 23. The belt conveyor 25 has clearances through which thesteam resulting from the piece of laundry can escape to the inner space7 of the hood and from there through the exhaust connections 8.

It is possible to create many variations of the contact press 26. Forinstance it is possible to build the heating plate 23 as a convex arch,whereby the pressure rollers 24 can be eliminated. The same situationcan occur in the case of so-called ironing press, in which a paddedcushion similar to the roller wrapping 3 (FIGS. 1 and 3) is positionedagainst the piece of laundry and presses it against a heating plate ofany desired shape.

FIG. 5 also shows a variation of the seals 9. The left side seal of thehood 6 is built as a roll seal which is pressed against the returnpulley of the belt conveyor 25. The roll seal consists of a flexible orremovably pivoted sealing roll, which is especially advantageous whenmounted at the entrance side of the mangle or another type of contactpress. This way it is possible also to position the roll seal againstthe return pulley of the feeding conveyor 18 (in FIG. 5) and to lift itshortly when a laundry piece comes in.

Such a roll seal can also be mounted at the exit side of the machine. InFIG. 5 a lip seal 9, different from the seals shown in FIGS. 1 to 3, ismounted at the exit side of the contact press 26. This lip sealpositions itself against the piece of laundry 11, respectively theheating plate 23.

The sealing of hood 6 on all sides leads to the fact that its innerspace during mangling, ironing, pressing or the like is essentiallyfilled only with steam. The steam arriving at the exhaust connections 8is an energy carrier of high value, which should be utilized with thepurpose of energy savings. The prior art uses the steam absorbed throughthe shaft of the roller for preheating the air fed to the mangle bed.This measure, as aforementioned, is based on the concept that extra airhas to be supplied for mangling, does not give satisfactory energysavings.

FIG. 4 shows the heat recovery process according to the invention andthe related equipment. From a washer 17 the wet laundry 11 is dischargedonto a conveyor 18 and is mechanically wrung, in this instance by adevice not represented in the drawing. From the conveyor 18 the laundrypiece 11 passes over a known type of feeding conveyor into the mangle 1.The mangle 1 can obviously also be an ironing machine, a press or thelike. The steam generated in the inner space 7 of the sealed hood 6reaches the exhaust connection 8 through a duct 15. In this duct 15 aseparator not shown in the drawing can be mounted, which separates thesteam from possibly entrained air. Further in the path of the duct 15 acompressor or a high-pressure blower 19 is mounted which feeds the steamfurther through the duct and compresses it into the washing fluid of thewashing machine 17. For the start-up of the installation when no laundryis mangled, pressed or ironed, and no steam is yet available adisconnectable fresh-steam duct 22 is provided which discharges into thewashing fluid. As soon as enough steam is available in the hood 6 thisfresh-steam duct 22 is disconnected.

During the operation of such a washing installation there can bevariations in the feeding rate. In such a case, there can be forinstance too little laundry or no laundry pieces 11 at all in the mangle1 and therefore only little or no steam is generated in the hood 6. Thecompressor, respectively the blower 19 exhausts at the same power,creating thereby a negative pressure in the inner hood space 7, leadingto an undesirable supply of infiltrated air. As aforementioned in thedescription of FIGS. 1 to 3, it is the purpose of the hood seal tocreate in the inner space 7 of the hood a pressure at least equal orslightly higher than the one outside the hood 6. In order to be able toautomatically control the steam absorption with respect to the availableamount of steam, a pressure sensor 13 is provided in the inner space 7of the hood which monitors the inner pressure and in case this dropsbelow an established level activates the damper 14 in the feeding duct15 and reduces thereby the existing suction pressure. Instead of thedamper 14, the compressor, respectively blower 19 can be controlled. Assoon as the inner hood pressure rises again due to a supply of laundry,the exhaust pressure is automatically raised.

In order to ensure the heating of the washing fluid while the mangle 1supplies insufficient steam the embodiment of FIG. 4 provides, inaddition to the fresh-steam duct 22 another auxiliary device, which canbe mounted instead or parallel to the fresh-steam duct 22. The heatingof the trough-shaped shaped hollow body 4, respectively of a heatingplate of different shape, takes place in this case in the presence ofhigh-pressure steam supplied from an external boiler, not shown, via asteam duct 20. With such a high-pressure steam heating system condensateis produced at a temperature of 180° C., for instance, which isevacuated via a condensate pipe 21. Through pressure drop and exteriorcooling a condensate having an approximate temperature of 100° C. isproduced here. The condensate pipe 21 can be now discharged directly inthe washing machine 17 and serve for the heating of the washing fluid.In addition, this condensate pipe 21 is led into or around the supplyduct 15, whereby the condensate yields heat to the low-pressure steam inthe hood 6. This way, an additional heating of the low-pressure steam inthe case of insufficient amounts of laundry in the mangle is obtained.On the other hand, this also prevents the condenation of possibleresidual steam in the anyway isolated duct 15. The feeding duct 15 alsohas an outlet 16 for the evacuation of water, when necessary.

In connection with the heat recovery, it is advisable to build thesealed hood 6, already described in the embodiments of FIGS. 1 to 3 and5, as large as possible. This has the advantage that in the case ofvariations in the supply rate with laundry pieces, the large inner space7 of the hood works as a buffer for the evacuation of the steam andprevents a too frequent adjustments of the existing exhaust pressure.

In the hood 6 a closable ventilation damper (not shown) is mounted,which is opened soon before the mangle or ironing press or the like isshut down. This air supply together with the blower 19 still inoperation allows for a complete evacuation of the steam contained in thehood 6, which otherwise would form into a condensate and drop down inthe mangle. Obviously, during normal operation this ventilation damperis closed in an airtight manner.

I claim:
 1. A method of mangling wet laundry which comprises the stepsof:closely juxtaposing a heated trough-shaped surface with a portion ofthe periphery of a roller covered with a steam-permeable wrapping;rotating said roller to draw said wet laundry along said surface whilepressing said wet laundry with said wrapping against said surfacewhereby steam is genrated by the contact of said surface with said wetlaundry, said steam penetrating into the wrapping of said roller;sealingly enclosing at least most of the balance of the periphery ofsaid roller in a hood and evacuating said hood to withdraw steampenetrating into said hood through said wrapping upon generation bycontact of said wet laundry with said surface; and substantiallycompletely excluding ambient air from penetrating into said hood whileevacuating steam therefrom by maintaining the pressure in the hood at apressure equal to or only slightly above ambient pressure whereby thesteam evacuated from said hood is substantially free from air.
 2. Themethod defined in claim 1, further comprising the step of directlyinjecting steam evacuated from said hood into a washing liquid to heatsaid washing liquid, and washing laundry to be subsequently mangledbetween said roller and said surface with the thus heated washingliquid.
 3. An apparatus for mangling wet laundry, comprising:at leastone mangling roller rotatable about its axis and covered with asteam-permeable pressing wrapping; a trough formed with a heated surfaceclosely juxtaposed with a portion of the circumference of said rollerwhereby wet laundry is entrained upon rotation of said roller betweensaid wrapping and said surface and is pressed while steam is generatedby the heating of said laundry by said surface, said steam penetratinginto said wrapping; a hood closing substantially the remainder of thecircumference of said roller and provided with exhaust means maintainingthe pressure in said hood equal to or only slightly above ambientpressure for drawing off steam from said hood; and seal means betweensaid hood and said wrapping for excluding the incursions of air intosaid hood while permeating steam penetrating through the wrapping to bedrawn off by said hood substantially free from the incursions of ambientair.
 4. The apparatus defined in claim 3 wherein a plurality of suchrollers each having a respective wrapping and juxtaposed with a heatedsurface of a respective trough are encompassed by said hood.
 5. Theapparatus defined in claim 4 wherein said rollers define a path for saidlaundry from an input side to an output side, said hood being providedwith an exhaust device at said input side.
 6. An apparatus for manglingwet laundry, comprising:at least one mangling roller rotatable about itsaxis and covered with a steam-permeable pressing wrapping; a troughformed with a heated surface closely juxtaposed with a portion of thecircumference of said roller whereby wet laundry is entrained uponrotation of said roller between said wrapping and said surface and ispressed while steam is generated by the heating of said laundry by saidsurface, said steam penetrating into said wrapping; a hood closingsubstantially the remainder of the circumference of said roller andprovided with exhaust means for drawing off steam from said hood; andseal means between said hood and said wrapping for excluding theincursions of air into said hool while permeating steam penetratingthrough the wrapping to be drawn off by said hood substantially freefrom the incrusions of ambient air, said sealing means including atleast one sealing lip bearing against said wrapping.
 7. An apparatus formangling wet laundry, comprising:at least one mangling roller rotatableabout its axis and covered with a steam-permeable pressing wrapping; atrough formed with a heated surface closely juxtaposed with a portion ofthe circumference of said roller whereby wet laundry is entrained uponrotation of said roller between said wrapping and said surface and ispressed while steam is generated by the heating of said laundry by saidsurface, said steam penetrating into said wrapping; a hood closingsubstantially the remainder of the circumference of said roller andprovided with exhaust means for drawing off steam from said hood; andseal means between said hood and said wrapping for excluding theincursions of air into said hool while permeating steam penetratingthrough the wrapping to be drawn off by said hood substantially freefrom the incursions of ambient air; means for injecting steam withdrawnby said hood from said wrapping into a washing liquid and forintroducing said washing liquid into a washing machine, said meansincluding a compressor; and a pressure sensor in said hood and a dampercontrolled by said pressure sensor between said hood and said washingmachine.
 8. The apparatus defined in claim 7 wherein the last mentionedmeans includes a compressor.
 9. The apparatus defined in claim 8,further comprising a pressure sensor in said hood and a dampercontrolled by said pressure sensor between said hood and said washingmachine.
 10. The apparatus defined in claim 8, further comprising afresh steam duct for introducing fresh steam into washing liquid in saidwashing machine.
 11. The apparatus defined in claim 8 wherein saidsurface is heated by steam, further comprising means for recoveringcondenstate from said trough and delivering to said washing machine aspart of said washing liquid.
 12. The apparatus defined in claim 11wherein the last mentioned means includes a condensate pipe and saidhood is connected to said washing machine by a steam duct, said duct andsaid condensate pipe being at least partially in exchanging contact withone another.
 13. The apparatus defined in claim 8 wherein said hood isprovided with a closable airtight ventilation damper.
 14. An apparatusfor washing and mangling laundry which comprises:a washing machinesupplied with a washing liquid; a mangle for receiving laundry from saidwashing machine, said mangle including:at least one roller provided witha steam-permeable pressing wrapping, a trough closely juxtaposed with aportion of the circumference of said roller and having a heated surfacejuxtaposed with said wrapping whereby rotation of said roller entrainswet laundry between said wrapping and said surface to press said laundryagainst said surface and generate steam which penetrates into saidwrapping, and a hood extending over substantially all of the balance ofsaid circumference and sealed with respect to said wrapping whereby saidhood collects steam pressing through said wrapping while excludingambient air therefrom; a duct connecting said hood with said washingmachine for introducing said steam into said washing liquid, said ductincluding means for evacuating said steam from said hood, said surfacebeing heated with steam introduced into said trough whereby condensateis formed from the heating steam; and a condensate-collecting pipeconnected to said trough and in heat-exchanging relationship with saidduct for introducing collected condensate into said washing machine aspart of said washing liquid.
 15. The apparatus defined in claim 14wherein said duct is provided with a damper controlled by said pressuresensor in said hood.
 16. The apparatus defined in claim 15, furthercomprising means between said washing machine and said mangle fortransferring wet laundry from said washing machine to said mangle.
 17. Amethod of pressing wet laundry which comprises the steps of:closelyjustaposing a heated surface with a steam-permeable wrapping; pressingsaid wet laundry against said surface with said wrapping whereby steamis generated by the contact of said surface with said wet laundry, saidsteam penetrating into the wrapping; sealingly justaposing said wrappingwith a hood and evacuating said hood to withdraw steam penetrating intosaid hood through said wrapping upon generation by contact of said wetlaundry with said surface; and substantially completely excludingambient air from penetrating into said hood while evacuating steamtherefrom by maintaining the pressure in the hood at a pressure equal toor only slightly above ambient pressure whereby the steam evacuated fromsaid hood is substantially free from air.